This invention relates to the field of solid state watthour meters, and more particularly to the calibration of the registration of these meters.
In solid state watthour meters, the registration of the meter is indicative of the product of the meter reading and the watthour constant, corresponding to the energy measurement of the meter. Percent registration is the ratio of the actual registration of the meter to the true value of the quantity measured in a given time, expressed as a percentage. Percent error is the difference between its percent registration and one hundred percent. A low percent error registration is important to ensure accurate measurement of the AC electrical energy consumed by a customer and proper calculation of the charge for the electrical service.
In many prior art meters, changes in registration are accomplished by altering the rotational rate of the meter disk. In solid state watthour meters, calibration has been achieved using a potentiometer to, in essence, vary the watthour constant for the meter. However, potentiometers are typically expensive and susceptible to reliability and stability problems.
In view of these difficulties, it is an object of the present invention to provide means for calibrating the registration of a watthour meter that is inexpensive, yet reliable. Another object is to provide a means for calibration that is stable, particularly in the harsh temperature environment of the watthour meter. An additional object is to provide a means for registration that is readily and easily accessible for the meter technician or customer. Other objects and benefits of the present invention will be observed in the following disclosure and accompanying figures.